Lithium battery, method for manufacturing a lithium battery, integrated circuit and method of manufacturing an integrated circuit

ABSTRACT

A lithium battery includes a cathode, an anode including a component made of silicon, a separator element disposed between the cathode and the anode, an electrolyte, and a substrate. The anode is disposed over the substrate or the anode is integrally formed with the substrate.

BACKGROUND

With the increased use of portable electronic devices such as notebooks,portable telephones, cameras and others and with the increased use ofcurrent-driven automobiles, lithium ion secondary batteries with highenergy density have received increasing attention as a power source forthese devices.

Conventionally, lithium ion secondary batteries comprise a positiveelectrode comprising a lithium-containing transition metal oxide or thelike, a negative electrode comprising a carbon material, and anon-aqueous electrolyte as well as a separator which is disposed betweenthe positive and the negative electrode.

In order to meet the increasing demands on capacity and performance, itis desirable to develop new anode materials, so that the energy storagecapacity of the battery can be increased and the resulting lithiumbattery can be manufactured in a simple manner.

Further, integrated circuits or electronic devices requiring arelatively low amount of electrical energy are increasingly used in manyapplications. It would be desirable to provide a miniaturized batterythat supplies these integrated circuits or electronic devices withenergy.

SUMMARY

According to an embodiment of a lithium battery, the lithium batterycomprises a cathode, an anode comprising a component made of silicon, aseparator element disposed between the cathode and the anode, anelectrolyte, and a substrate. The anode is disposed over the substrateor the anode is integrally formed with the substrate.

According to an embodiment of a method of manufacturing a lithiumbattery, the method comprises: forming an anode on a surface of asubstrate; forming a separator element; forming a cathode so that theseparator element is disposed between the cathode and the anode; andfilling an electrolyte in a space formed by the anode, the cathode andthe substrate.

According to an embodiment of an integrated circuit, the integratedcircuit comprises a circuit element formed in a semiconductor substrateand a lithium battery. The lithium battery comprises an anode comprisinga component made of silicon and a substrate. The lithium battery isformed in the substrate or in a layer over the substrate.

According to an embodiment of a method of manufacturing an integratedcircuit, the method comprises: forming a circuit element in asemiconductor substrate; and forming a lithium battery. The lithiumbattery is formed by forming an anode on a surface of the semiconductorsubstrate or in a semiconductor layer over the semiconductor substrate.

According to another embodiment of a method of manufacturing a lithiumbattery, the method comprises: forming a circuit element in a firstsemiconductor substrate; forming a lithium battery by forming an anodeon a surface of a second semiconductor substrate; and packaging thefirst semiconductor substrate and the second semiconductor substrate ina common housing.

According to an embodiment of an electronic device, the electronicdevice comprises an electric circuit and a lithium battery. The lithiumbattery comprises a cathode, an anode comprising a component made ofsilicon, a separator element disposed between the cathode and the anode,an electrolyte, and a substrate. The anode is disposed over thesubstrate or integrally formed with the substrate.

According to another embodiment of an electronic device, the electronicdevice comprises an electric circuit and an integrated circuit. Theintegrated circuit comprises a circuit element formed in a semiconductorsubstrate and a lithium battery. The lithium battery comprises an anodecomprising a component made of silicon and a semiconductor substrate.The lithium battery is formed in the semiconductor substrate or in alayer over the semiconductor substrate.

Those skilled in the art will recognize additional features andadvantages upon reading the following detailed description, and uponviewing the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of embodiments of the invention and are incorporated inand constitute a part of this specification. The drawings illustrate theembodiments of the present invention and together with the descriptionserve to explain the principles. Other embodiments of the invention andmany of the intended advantages will be readily appreciated, as theybecome better understood by reference to the following detaileddescription. The elements of the drawings are not necessarily to scalerelative to each other. Like reference numbers designate correspondingsimilar parts.

FIG. 1A shows a cross-sectional view of a lithium battery;

FIG. 1B shows a cross-sectional view of a lithium battery according toan alternative embodiment;

FIG. 2A shows a cross-sectional view of an integrated circuit comprisinga lithium battery;

FIG. 2B shows a top view of an integrated circuit comprising a lithiumbattery;

FIG. 3 shows an electronic device according to an embodiment;

FIG. 4 shows an electronic device according to an embodiment;

FIG. 5 shows an electronic device according to an embodiment;

FIGS. 6A and 6B show a cross-sectional view and a top view of a carrierwhen performing a method of manufacturing a lithium battery;

FIGS. 7A and 7B illustrate a cross-sectional view and a top view of acarrier after forming a groove in the carrier;

FIG. 8 shows a cross-sectional view of a carrier after performing afurther processing step;

FIG. 9 shows a cross-sectional view of an example of a carrier includinga groove;

FIG. 10 shows a cross-sectional view of a carrier after performing afurther processing step;

FIG. 11 schematically illustrates a method of forming a lithium battery;

FIG. 12 schematically illustrates a method of manufacturing anintegrated circuit; and

FIG. 13 shows an example of an electronic device including a battery.

DETAILED DESCRIPTION

In the following detailed description reference is made to theaccompanying drawings, illustrating specific embodiments in which theinvention may be practiced. In this regard, directional terminology suchas “top”, “bottom”, “front”, “back”, “leading”, “trailing” etc. is usedwith reference to the orientation of the Figures being described. Sincecomponents of embodiments of the invention can be positioned in a numberof different orientations, the directional terminology is used forpurposes of illustration and is in no way limiting. It is to beunderstood that other embodiments may be utilized and structural orlogical changes may be made without departing from the scope defined bythe claims.

The terms “carrier” or “semiconductor carrier” used in the followingdescription may include any semiconductor-based structure that has asemiconductor surface. Carrier and structure are to be understood toinclude silicon, silicon on insulator (SOI) silicon-on-saphire (SoS),doped and undoped semiconductors, epitaxial layers of silicon supportedby a base semiconductor foundation, and other semiconductor structures.Further, the term “carrier” or “semiconductor carrier” further comprisesany kind of semiconductor layer, which may be crystalline,polycrystalline or amorphous, which is formed on a suitable substratematerial. In addition, the carrier may comprise an insulator. Specificexamples comprise glass such as quartz glass (SiO₂), ceramics orpolymers. Further, the term “substrate” may as well include anysemiconductor-based structure that has a semiconductor surface. Thesemiconductor need not be silicon-based. The semiconductor could as wellbe silicon carbide, silicon-germanium, germanium, germanium or galliumarsenide. The substrate may comprise a semiconductor or an insulator.Specific examples comprise glass such as quartz glass (SiO₂), ceramicsor polymers.

The terms “connected” or “interconnection” as used within the context ofthe present specification mean that the respective components may be insignal connection to each other. For example, further elements may bedisposed between the components. Further, the respective components neednot be physically connected as long as signals may be exchanged betweenthem. Moreover, the terms “connected” and “interconnection” alsoencompass the case in which, for example, a voltage is not applied.

FIG. 1A shows a cross-sectional view of an example of a lithium battery2. The cross-sectional view is taken between II and II as is shown inFIG. 6B.

The lithium battery shown in FIG. 1A comprises a cathode 13, an anode 17comprising a component made of silicon, a separator element 18 disposedbetween the cathode 13 and the anode 17, an electrolyte 12, and asubstrate 19, the anode 17 being disposed over the substrate 19. Forexample, the anode 17 may be integrally formed with the substrate 19.Alternatively, the anode 17 may be an additional layer that is formedover the substrate 19. The anode 17, the separator element 18 and theelectrolyte 12 may be arranged in a groove 31 that is disposed in thesilicon body 1. For example, the anode 17 may form a wall of the groove31. The groove 31 may comprise side walls and a bottom side and theanode 17 may form the bottom side of the groove 31. The anode 17 mayfurther comprise a thin metal layer 11.

The substrate 19 may be made of any material as described above. Thesubstrate 19 may be patterned. Accordingly, as is shown in FIG. 1A, agroove 31 may be formed in the substrate 19. The anode 17 may comprisesilicon material which may be monocrystalline, polycrystalline oramorphous. The silicon material may be doped with any dopant as isconventionally used such as boron (B), arsenic (As), phosphorus (P) orantimony (Sb). The active silicon surface of the anode 17 may be planaror may be patterned. For example, three-dimensional structures such aspyramids, trenches and columns may be formed in the surface of theanode. A thin metal layer 11 may be formed over the surface of the anode17 that contacts the electrolyte 12. For example, the metal layer 11 maycomprise silver (Ag), aluminum (Al), gold (Au), palladium (Pd) orplatinum (Pt). Metals, that form an alloy with lithium, may be used.Further examples comprise Zn, Cd, Hg, B, Ga, In, Th, C, Si, Ge, Sn, Pb,As, Sb, Bi, Se, and Te. A thickness of the metal layer 11 may be lessthan 100 nm and, for example, more than 1 nm. For example, Ag forms analloy with Li at a voltage of approximately 500 mV, whereas Si forms analloy at a voltage of approximately 330 mV. Therefore, when applying anAg-metal layer, an Ag—Li alloy will be formed at the surface of theanode 17 before charging the Si material with lithium so that the Liions will move to the Si anode in a homogeneous manner. Further, due tothe alloy layer, the formation of the native SiO₂ layer on the anodesurface is prevented so that the transportation of ions is furtherenhanced. In addition, the insertion of Li atoms in the Si anode will beaccomplished in a more homogeneous manner so that the performance of thelithium battery will be improved. Moreover, due to the presence of thethin metal layer the mechanical stability of the electrode duringcharging and discharging is enhanced.

It has been observed that the charging time will be increased during thefirst charging cycle. This may be due to the thin metal layer 11 whichis present on the surface of the anode 17. Nevertheless, after a numberof charging cycles, the charging velocity will be equal to the case ofemploying an anode without a metal layer.

For the cathode 13, generally known electrical materials that are usedin lithium ion batteries may be employed. Examples comprise LiCoO₂,LiNiO₂, LiNi_(1-x)Co_(x)O₂, LiNi_(0.85)Co_(0.1)Al_(0.05)O₂,LiNi_(0.33)CO_(0.33)Mn_(0.33)O₂, LiMn₂O₄ spinel and LiFePO₄. Theelectrolyte 12 may include electrolytes commonly used for lithiumbatteries such as salts such as e.g. LiPF₆, LiBF₄ in water-free aproticsolvents such as propylene carbonate, dimethylcarbonate or1,2-dimethoxymethane, ethylene carbonate, diethyl carbonate and others,polymers, for example polyvinylidenefluoride (PVDF) orpolyvinylidenefluoride hexafluorpropene (PVDF-HFP) or other polymers,Li₃PO₄N and others.

The separator 18 spatially and electrically separates the anode 17 andthe cathode 13 from each other. Nevertheless, the separator 18 must bepermeable for the ions so that a conversion of the stored chemicalenergy into electrical energy may be accomplished. Examples of thematerial of the separator 18 comprise non-woven fabric made of materialssuch as fiberglass, polyethylene or micro porous materials. Further,membranes which are made of microporous sheet that may comprise severallayers may be employed. Further examples comprise non-woven fabric whichis coated with a ceramic material. Further examples are well known inthe art.

A sealant 14 may be formed over the cathode 13. The sealant 14 providesa water and airtight capsulation. Examples of the material of thesealant 14 comprise well-known polymers e.g. polyimide. A passivationlayer 10 is formed over those parts of the silicon body 1 which do notform the anode 17. To be more specific, the side walls of the groove 31are covered with a passivation layer 10. Further, the outside of thesubstrate 19 or the housing of the battery is covered with thepassivation layer 10. The passivation layer 10 may comprise differentmaterials such as silicon oxide (SiO₂), silicon nitride (Si₂N₄),polymers, imids, spin-on-glass (SOG), polyethylene, metals or anycombination of these materials, for example a layered structure ofpolymers and metals. The passivation layer 10 prevents a diffusion oflithium atoms to neighboring components.

Conductive layers 15, 16 are formed on the back side of the battery 2.For example, a metal layer 16 such as copper may be formed on the backside, an interface layer 15 such as TiW being disposed between the anodematerial 17 and the copper layer 16. For example, the thickness of theinterface layer 15 may be in the range of 50 to 150 nm, for example, 100nm. Further, the thickness of the copper layer 16 may be more than 500nm, for example 1 μm or more. Alternatively, the current may as well bedischarged using a buried layer or channel, for example made ofpolysilicon or doped silicon.

The battery 2 may be a rechargeable or secondary lithium ion battery.According to a further embodiment, the battery 2 may be a primarybattery which is not rechargeable.

The battery 2 shown in FIG. 1A has an improved capacity for energystorage, since silicon has a large capacity of insertion of lithium. Inother words, the amount of lithium atoms that can be stored or insertedin silicon is much larger than in conventional cases. Since the anode 17comprises silicon, silicon or general semiconductor processing methodsmay be employed. In particular, methods for manufacturing miniaturizedsizes can effectively be applied for manufacturing a battery having asmall size in comparison to conventional batteries. According toembodiments, the packaging comprises materials that are known fromsemiconductor processing such as glass or mold compound. According tofurther embodiments, the anode 17 is integrated with the substrate 19.In these cases, also semiconductor processing methods may be employed inorder to further miniaturize the battery 2. According to knownsemiconductor processing methods, small-sized structures may be formedso that a faster, more homogeneous, and more efficient insertion oflithium in the silicon material can be achieved. Additionally, a highermechanical long term stability is given. Further, it is possible tointegrate additional components into a single die comprising the lithiumbattery.

As is shown in FIG. 1A, the anode 17 is disposed in a groove 31 formedin the silicon body 1. Optionally, the anode 17 further comprises athree-dimensional surface structure so that the active surface of theanode 17 is increased. Thereby, detrimental effects of an increase ofthe volume of silicon due to the lithiation can be prevented. Moreover,due to the presence of the separator 18, the increase of the volume ofsilicon is buffered, so that the mechanical stress due to the lithiationis reduced. In the structure shown in FIG. 1A, the substrate 19 formsthe housing 34 of the battery 2. According to an embodiment, the anode17 may be integrally formed with the substrate 19 and the housing 34.

FIG. 1B shows a cross-sectional view of a further example of a lithiumbattery 2. The cross-sectional view may be taken between II and II as isshown in FIG. 3B, for example.

The lithium battery 2 shown in FIG. 1B comprises a cathode 13, an anode17 comprising a component made of silicon, a separator element 18disposed between the cathode 13 and the anode 17, an electrolyte 12,that are formed on a substrate 19. The substrate 19 may be patterned.For example, a plurality of grooves or columns may be formed in thesubstrate 19. For example, the grooves or columns may be formed byetching. Alternatively, the grooves or columns may be selectively grownover a planar surface so as to form extending portions 19 a. Theextending portions 19 a may have a depth d with respect to a planarsurface of the substrate 19, wherein the depth d is 20 to 100 μm. Thesubstrate 19 may be made of any substrate material as mentioned above.The grooves or columns need not have a rectangular cross-sectionalshape.

According to embodiments, also different shapes such as pyramids orothers may be employed.

The anode 17 may comprise a semiconductor layer 17 a, which may compriseany of the semiconductor materials as described above. The anode 17 maybe formed as a layer over the surface of the substrate 19. For example,in the battery portion of the substrate 19, the semiconductor layer 17 aforming the anode 17 covers the entire surface of the substrate 19.Nevertheless, as is clearly to be understood, according to a furtherembodiment, the substrate 19 may be a semiconductor substrate and thesurface portion of the substrate 19 forms the anode 17 of the resultingbattery 2. In a similar manner as has been explained above, a thin metallayer 11 may be formed over the surface of the anode 17 that contactsthe electrolyte 12. The materials of the metal layer 11 may be selectedfrom the materials described above. A thickness of the metal layer 11may be less than 100 nm, for example, more than 1 nm. The remainingcomponents of the battery 2 shown in FIG. 1B may be the same as that ofthe battery shown in FIG. 1A. The passivation layer 10 is formed on thesidewall portions of the substrate 19 and the battery 2. The cathode 13is formed over the separator 18 so as to enclose the electrolyte 12. Asealant 14 may be formed over the cathode 13 as has been explainedabove.

FIGS. 2A and 2B show an integrated circuit 36 including a battery 2 andcircuit elements 20. The cross-sectional view of FIG. 2A is takenbetween III and III as is shown in FIG. 2B. In FIG. 2A, the battery 2may have a structure similar as the structure shown in FIGS. 1A and 1B.Further, the circuit elements 20 may be formed in or on a semiconductorsubstrate 1. For example, the circuit elements 20 may comprisetransistors, resistors, capacitors, MEMS (micro-electro-mechanicalsystem) devices, sensors, energy harvesters, for example, devices whichderive energy from external sources (e.g. solar power, thermal energy,wind energy, salinity gradients and kinetic energy), a device forreceiving energy, a device for converting energy such as a solar cell,for example, a device for emitting energy such as RFIDs (radio frequencyidentification devices), a display device, a video device or an audiodevice, a music player, a signal processing circuit, an informationprocessing circuit, an information storage circuit, or components of anyof these devices and others. Further examples of circuit elements 20comprise circuits that control a charging or discharging process. Forexample, the circuit element 20 may be configured to control charging ofthe battery 2 so that charging is stopped before its complete storagecapacity has been reached. The circuit elements 20 may be formed in thesemiconductor substrate 1 or they may be formed in layers positionedover the semiconductor substrate. The battery 2 may be formed in thesame semiconductor substrate 1. Alternatively, the battery 2 may beformed in a layer placed over the semiconductor substrate 1. An elementseparation trench 30 may be formed between the battery 2 and the circuitelement 20 in order to prevent diffusion of lithium atoms to theintegrated circuit 3. The element separation trench 30 may be filledwith the materials of the passivation layer 10 as mentionedhereinbefore. Depending on the manufacturing method employed, thepassivation layer 10 and the element separation trench 30 of theintegrated circuit 36 may be made of the same layers.

FIG. 2B shows a top view of the integrated circuit 36 shown in FIG. 2A.The battery 2 is enclosed by an element separation trench 30 which maybe filled with silicon oxide and/or silicon nitride. In the peripheralportion of the die, integrated circuits 3 are illustrated. As is clearlyto be understood, FIG. 2B shows only an example of an arrangement andfurther suitable arrangements are easily conceivable. According to anembodiment, a sensor or another component utilizing energy may beimplemented by one integrated circuit 3. Further, an energy harvestermay be implemented by another integrated circuit 3. With thisconfiguration, electrical energy for driving the sensor may be generatedand stored in the integrated circuit 36. A kerf 35 may be disposed atthe edge of the integrated circuit 36. Several of these integratedcircuits 36 may be connected in series. Soldering pads may be disposedoutside the housing of the integrated circuit 36.

FIG. 3 shows an embodiment of an electronic device 50, in which severalchips are arranged within one layer and housed by one housing 55. Inother words, according to this configuration, several componentsincluding the battery are packaged by a common package. However, theyare not monolithically integrated. As is shown, on a side of a carriersubstrate 54, several chips, for example, comprising a battery substrate51 in which a battery as has been shown in FIG. 1A or 1B is disposed andan integrated circuit (IC) substrate 53 may be arranged. Intermediateelements 52 a, 52 b, 52 c which may comprise, for example, an insulatingmaterial such as a polymer, a ceramic or others may be disposed betweenthe battery substrate 51 and the IC substrate 53. Circuit elements 20 ashave been described above with reference to FIG. 2A may be disposedwithin the IC substrate 53. The battery substrate 51 and the ICsubstrate 53 are physically connected with each other by means of thecarrier substrate 54. Further, conductive lines may be disposed withinthe carrier substrate so as to enable an electrical contact betweenthese components. For example, the carrier substrate 54 may be made ofany suitable substrate material or of an insulating substrate materialsuch as a ceramic, a polymer and others. A thickness of the carriersubstrate 54 may be 20 to 100 μm. A thickness of the battery substrate51 and the IC substrate 53 may be approximately 200 μm. The size of theelectronic device 50 shown in FIG. 3 may, for example, be approximatelysimilar to the size of a semiconductor chip, in the range of 1×1 mm² toseveral hundred mm², for example, 4×4 mm² or 5×5 mm². Typical storagecapacities of such a battery having a size of 4×4 mm² may be in theorder of about 10 mAh. According to an embodiment, a sensor or anothercomponent utilizing energy may be disposed in the IC substrate 53,whereas a battery is disposed in the battery substrate 51 and an energyharvester is disposed in the IC substrate 53 or a further integratedcircuit substrate. With this configuration, electrical energy fordriving the sensor may be generated and stored in the electronic device50 which also includes the sensor.

FIG. 4 shows a further example of an electronic device 60. Theelectronic device 60 comprises a first substrate 61 and a secondsubstrate 62. A battery as has been described above with respect to FIG.1A or 1B is disposed within the first substrate 61. Electric circuits,for example, integrated circuits comprising circuit elements 20 as havebeen described above with reference to FIG. 2A may be disposed withinthe second substrate 62. In addition, such components or circuitelements may also be disposed within the first substrate 61. Forexample, some electric circuits may be disposed within the firstsubstrate 61 and additional integrated circuits or circuit elements maybe disposed within the second substrate 62. The first and secondsubstrates 61, 62 may be disposed in one layer. Nevertheless, they mayas well be disposed in different layers. For example, they may bestacked. The first and second substrates 61, 62 may have the same ordifferent sizes. The first and second substrates and/or elements of thefirst and second substrates 61, 62 may be interconnected by means of oneor more contact wires 63. They may be housed by a housing 65. Further,the components inside the housing 65 of the electronic device 60 may beaccessible via contacts 64. The specific arrangement of the componentswithin the electronic device 60 may, for example, depend on the specificconditions for use and the specific implementations of the electronicdevice 60. According to an embodiment, a battery is disposed in thefirst substrate 61, a sensor or another component utilizing energy maybe disposed in the second substrate 62, and an energy harvester may bedisposed in the first or the second substrate 61, 62. With thisconfiguration, electrical energy for driving the sensor may be generatedand stored in the electronic device 60 which also includes the sensor. Atypical size of the electronic device 60 is about 1×1 to several 100mm², for example less than 10×10 mm².

FIG. 5 shows a further embodiment of an electronic device 70. Theelectronic device 70 comprises a first battery 71 a and, optionally, asecond battery 71 b. As is clearly to be understood, the electronicdevice 70 may comprise more than two batteries. The first and the secondbatteries 71 a, 71 b are housed by separate housings 72 a, 72 b.Further, the first and second batteries 71 a, 71 b are connected witheach other. The electronic device 70 further comprises an electroniccomponent 74 which is housed by a separate housing 73. Examples of theelectronic component 74 comprise any kinds of electric devices orcircuit elements 20 as mentioned above. Further examples of theelectronic component 74 comprise a computer, for example, a personalcomputer, or a notebook, a server, a router, a game console, forexample, a video game console, as a further example, a portable videogame console, a graphics card, a personal digital assistant, a digitalcamera, a cell phone, an audio system such as any kind of music player,a video system or a transportation device such as a car, a motorbike, apersonal transporter or any kind of appliance that may bebattery-driven. Further examples of electronic devices that may bebattery-driven are easily conceivable to the person skilled in the art.For example, the electronic device 74 may be a portable or anon-portable electronic device. According to the arrangement shown inFIG. 5, the batteries 71 a, 71 b as well as the electronic component 74are separately housed and may be assembled so as to form a functionableelectronic device 70. A typical size of the electronic device 70 is, forexample, in the range of 1×1 to several hundred mm².

FIGS. 6 to 10 illustrate an example of a process of manufacturing thebattery and/or an integrated circuit.

The process described in the following uses several methods that arewell known in semiconductor technology. Accordingly, any of the stepsperformed with respect to the manufacturing of the battery can as wellbe used for processing an integrated circuit that may be formed on thesame chip. The example shown in FIGS. 6 to 10 illustrates the steps ofmanufacturing the battery elements only. Nevertheless, as is clearly tobe understood, the employed processes or a part of them may as well beused for processing the circuit elements, although not being explicitlyshown in the drawings.

FIG. 6A shows a cross-sectional view of a portion of a carrier, and FIG.6B shows a plan view of the carrier. The cross-sectional view of FIG. 6Ais taken between I and I as shown in FIG. 6B. In the following Figures,also cross-sectional views between II and II are shown as is illustratedin FIGS. 6A and 6B. Separation trenches 30 are formed in the carrier.The separation trenches extend to such a large depth into the carrierthat the back side of the carrier may be thinned in a later processingstep so as to isolate neighboring batteries from each other using theseparation trenches 30. The separation trenches are formed usinggenerally known processing methods including lithographic methods fordefining the position of the separation trenches and etching by knownprocesses including dry-etching or wet-etching as is generally known inthe art of semiconductor processing. FIG. 6B shows an example of a planview. As is shown in FIG. 6B the separation trench encloses a centralportion of the carrier portion 1. Although the shown separation trench30 has a rectangular shape any other shape can be taken. In particular,the separation trenches may be formed as vertical and horizontalcontinuous lines so as to form a mesh. The width of each of theseparation trenches 30 may be chosen so that the separation trenches 30may be suitable filled with the material forming the diffusion barrieras will be described later.

Thereafter, a groove 31 may be formed in the surface of the carrier 1.The groove 31 may be formed by generally known etching methods, forexample wet-chemical etching using KOH for providing inclined sidesurfaces of the groove depending on the crystal direction if a carrierof monocrystalline silicon is used. Nevertheless, as is clearly to beunderstood alternative etching methods may be employed. The depth of thegroove 31 may be selected so as to achieve a desired storage capacity ofthe battery. The bottom side of the groove 31 forms the active siliconsurface. FIG. 7A shows a cross-sectional view of the die between I and Iafter forming the groove 31, FIG. 7B shows a plan view of the die.

A passivation layer 10 which may have the function of a diffusionbarrier is formed over the surface of the carrier, while leaving thebottom side of the groove 31 uncovered. The passivation layer 10 maycomprise silicon oxide (SiO₂) and/or silicon nitride (Si₃N₄), polymers,imids, spin-on-glass (SOG), polyethylene or any combination of thesematerials. Further examples comprise metals or combinations of metalsand the materials mentioned above. During the deposition of thepassivation layer 10, the bottom side of the groove 31 may be masked bya suitable material so as to prevent the deposition of the passivationlayer 10. The layer thickness may be adjusted to form a conformal lineror a filling in the separation trenches 30. For example, if theseparation trenches 30 are to be used for isolating single batteries ina later processing step, the passivation layer 10 can form a conformalliner. If, on the other hand, the separation trenches 30 are to be usedas an element isolation trench in a later processing step, thepassivation layer 10 can form a filling. FIG. 8 shows a cross-sectionalview of an example after forming the passivation layer 10 as a conformalliner.

Then, optionally, processing to form a three-dimensional structure inthe active surface may be performed so as to increase its surface area.This processing may comprise lithographic methods and patterning byetching processes, performing electrochemical processes, wet-chemicalprocesses, forming a native high temperature structure by using asuitable deposition process. Thereby, the insertion of Li ions isfacilitated and the mechanical expansion of the anode material due tothe insertion of lithium is compensated. For example, trenches,pyramids, columns and others may be formed on the bottom side of thegroove 31. For example, these steps may be performed using thepassivation layer 10 as a mask. FIG. 9 shows trench structures 32vertically extending from the bottom side of the groove 31. The trenchstructures 32 may have a depth d measured from the planar bottom side ofthe groove 31 of about 20 to 700 μm. Nevertheless, additionallysub-structures may be formed in the trench structures 32. For example,horizontally extending sub-structures may be formed in each of thetrench structures 32. As a further example, mesopores or others may beformed in the trench structures 32 so as to enhance the surface areathereof.

Thereafter, a thin metal layer 11 is formed over the exposed siliconmaterial forming the anode. The metal layer 11 may have a thicknessabout 10 to 100 nm. The material may comprise metals such as Ag, Al, Au,Pd or Pt, which have the possibilities of forming an alloy with lithium.Further examples comprise Zn, Cd, Hg, B, Ga, En, Th, C, Si, Ge, Sn, Pb,As, Sb, Be, Se, Te. The metal layer 11 may be formed by sputtering or byany other deposition process as is generally known. Thereafter, theseparator or separators stack 18 is formed in the groove 31. Theseparator or separator stack 18 may be formed by the methods that aregenerally known. Then, the electrolyte material 12 is filled into thegroove 31. This may also be accomplished by generally known methods.

Thereafter, the cathode 13 is arranged over the groove 31. Materials ofthe cathode 13 may comprise the examples as mentioned above. The cathode13 may be formed by generally known methods. Finally, the sealantmaterial 14 is formed over the surface of the cathode 13. Thereafter,the die will be thinned from the back side. For example, this may beaccomplished by chemical mechanical polishing (CMP) or etching. Due tothis thinning step, the single batteries can be isolated. However,alternative methods of isolation of the elements as e.g. sawing or lasercutting are possible. FIG. 10 shows an example of a cross-sectional viewafter isolation of the batteries.

Then the back side metallization is formed on the back side of thecarrier 1. For example, first an interfacial layer 15 of TiW may beformed by known methods, followed by a metal layer 16 such as copper orany other suitable conductive material. The metal layer 16 may have athickness of 500 nm to 50 μm.

Thereafter, the metal layer 16 may be patterned so as to form conductivelines for discharging the current produced by the battery.

Although steps for manufacturing a battery have been shown in FIGS. 6 to10, it is clearly to be understood that the method can be modified sothat an integrated circuit as shown in FIG. 2 can be manufactured. Forexample, for manufacturing an integrated circuit comprising a circuitformed in a semiconductor substrate and a lithium battery, the elementseparation trenches 30 (cf. FIG. 2A) can be formed so as to have a widthso that in the step of forming the passivation layer a filling isformed.

FIG. 11 shows a flow diagram illustrating an example of a method offorming a battery. As is shown, the method comprises forming an anode ona surface of a substrate (S11), forming a separator element (S21),forming a cathode (S31) so that the separator element is disposedbetween the cathode and the anode and filling an electrolyte in a spaceformed by the anode, the cathode and the substrate (S41). For example,forming the anode may comprise patterning a surface of the substrate byforming a groove in the substrate, wherein a wall of the groove formsthe anode. The method may further comprise forming a layer including ametal over at least a portion of the silicon body (S51).

FIG. 12 illustrates a method of manufacturing an integrated circuit. Asis shown, the method may comprise forming circuit elements in asemiconductor substrate (S2, S21, S22, S23) and forming a lithiumbattery (S3), wherein forming a lithium battery comprises forming ananode on a surface of the semiconductor substrate or in a semiconductorlayer over the semiconductor substrate (S31, S32, S33). Forming thecircuit elements (S21, S22, S23) in the semiconductor substrate andforming a lithium battery (S31, S32, S33) may comprise common processingsteps. For example, the respective methods may comprise common andnon-common processing steps. Accordingly, some of the processing stepsare performed subsequently, while other processing steps are performedconcurrently.

FIG. 13 schematically shows an electronic device 40 according to anembodiment. As is shown in FIG. 13, the electronic device 40 maycomprise an electric circuit 41, and a battery 42. The battery 42 may bea battery as has been described hereinabove, for example with referenceto FIGS. 1A and 1B. According to a further embodiment, the battery 42may be an integrated circuit as has been described with reference toFIGS. 2A and 2B, for example. To be more specific, the battery 42 mayadditionally comprise circuit elements 20 as is shown in FIG. 2A.Alternatively, the battery 42 and the electric circuit 41 may beimplemented on separate chips or dies as has been explained above withrespect to FIGS. 3 and 4. When the battery 42 and the electric circuit41 are disposed on separate chips, the battery 42 may be connected withthe electric circuit 41 via an interconnection 44. The electric circuit41 may comprise a processing device for processing data. The electriccircuit 41 may further comprise one or more display devices fordisplaying data. The electric circuit 41 may further comprise atransmitter for transmitting data. The electronic device 40 may furthercomprise components which are configured to implement a specificelectronic system. According to an embodiment, the electronic device 40may further comprise an energy harvesting device 43 that may deliverelectrical energy to the battery 42, the energy having been generatedfrom solar, thermal, kinetic or other kinds of energy. For example, theelectronic device 40 may be a sensor such as a tire pressure sensor,wherein the electric circuit 41 further comprises sensor circuitry and,optionally, a transmitter that transmits sensed data to an externalreceiver. According to another embodiment, the electronic device 40 maybe an actuator, an RFID tag or a smartcard. For example, a smartcard mayadditionally comprise a fingerprint sensor, which may be operated usingenergy delivered by the battery 42.

While embodiments of the invention have been described above, it isobvious that further embodiments may be implemented. For example,further embodiments may comprise any subcombination of features recitedin the claims or any subcombination of elements described in theexamples given above. Accordingly, this spirit and scope of the appendedclaims should not be limited to the description of the embodimentscontained herein.

What is claimed is:
 1. A lithium battery, comprising: a cathode; ananode comprising a component made of silicon; a separator elementdisposed between the cathode and the anode; an electrolyte; and asemiconductor substrate, the lithium battery being disposed over thesemiconductor substrate or integrally formed with the semiconductorsubstrate.
 2. The lithium battery according to claim 1, wherein a grooveis formed in the semiconductor substrate, and the anode, the separatorelement and the electrolyte are arranged in the groove.
 3. The lithiumbattery according to claim 2, wherein the anode forms a wall of thegroove.
 4. The lithium battery according to claim 2, wherein the groovecomprises sidewalls and a bottom side and the anode forms the bottomside of the groove.
 5. The lithium battery according to claim 1, whereinthe anode further comprises a layer including a metal disposed on a sideof the anode facing the electrolyte.
 6. The lithium battery according toclaim 1, wherein the anode is formed in a layer disposed over thesemiconductor substrate and wherein the layer forming the anodecompletely covers a portion of the semiconductor substrate in which thebattery is formed.
 7. The lithium battery according to claim 1, whereina surface of the semiconductor substrate is patterned.
 8. The lithiumbattery according to claim 7, wherein a plurality of grooves are formedin the surface of the semiconductor substrate.
 9. The lithium batteryaccording to claim 8, wherein the grooves have a depth of 20 to 100 μm.10. A method of manufacturing a lithium battery, comprising: forming ananode comprising a component made of silicon on a surface of asemiconductor substrate; forming a separator element; forming a cathodeso that the separator element is disposed between the cathode and theanode; and filling an electrolyte in a space formed by the anode, thecathode and the semiconductor substrate.
 11. The method of claim 10,wherein forming an anode comprises patterning a surface of thesemiconductor substrate by forming a groove in the semiconductorsubstrate, a wall of the groove forming the anode.
 12. The method ofclaim 11, wherein the groove comprises sidewalls and a bottom side andthe anode forms the bottom side of the groove.
 13. The method of claim10, wherein forming an anode comprises patterning a surface of thesemiconductor substrate by forming sub-structures in the surface of thesemiconductor substrate.
 14. The method of claim 10, further comprisingforming a layer including a metal over at least a portion of thesemiconductor substrate facing the electrolyte.
 15. An integratedcircuit, comprising: a circuit element formed in a semiconductorsubstrate; and a lithium battery comprising: an anode comprising acomponent made of silicon, wherein the lithium battery is formed in thesemiconductor substrate or in a layer over the semiconductor substrate.16. The integrated circuit of claim 15, wherein the lithium battery isformed in a semiconductor layer formed over the semiconductor substrate.17. The integrated circuit of claim 15, wherein the circuit element isselected from the group consisting of an energy receiving device, anenergy emitting device, a signal processing circuit, an informationprocessing circuit, an information storing circuit, a transistor, acapacitor, a resistor, a MEMS (micro-electro-mechanical system) device,a sensor, an actuator, an energy harvester, a device for convertingenergy, a display device, a video device, an audio device, a musicplayer and components of any of the devices.
 18. A method ofmanufacturing an integrated circuit, comprising: forming a circuitelement in a semiconductor substrate; and forming a lithium battery,wherein forming a lithium battery comprises forming an anode comprisinga component made of silicon, wherein the lithium battery is formed inthe semiconductor substrate or in a semiconductor layer over thesemiconductor substrate.
 19. The method of claim 18, wherein forming thelithium battery further comprises: forming a separator element; forminga cathode so that the separator element is disposed between the cathodeand the anode; and filling an electrolyte in a space formed by theanode, the cathode and the semiconductor substrate or semiconductorlayer.
 20. The method of claim 18, wherein forming the circuit elementand forming the lithium battery comprises common processing steps.
 21. Amethod of manufacturing an integrated circuit, comprising: forming acircuit element in a first semiconductor substrate; forming a lithiumbattery, including forming an anode comprising a component made ofsilicon, the anode being formed in a surface of a second semiconductorsubstrate; and packaging the first semiconductor substrate and thesecond semiconductor substrate in a common housing.
 22. The method ofclaim 21, wherein the first and second semiconductor substrates arearranged in one layer.
 23. The method of claim 21, wherein the first andsecond semiconductor substrates are stacked.
 24. An electronic devicecomprising: an electric circuit; and a lithium battery, the lithiumbattery comprising: a cathode; an anode comprising a component made ofsilicon; a separator element disposed between the cathode and the anode;an electrolyte; and a substrate, the anode being disposed over thesubstrate or being integrally formed with the substrate.
 25. Theelectronic device according to claim 24, wherein the electronic deviceis selected from the group consisting of a sensor, an actuator, an RFID(radio frequency identification device) tag and a smartcard.
 26. Anelectronic device, comprising: an electric circuit; and an integratedcircuit comprising: a circuit element formed in a semiconductorsubstrate; and a lithium battery comprising: an anode comprising acomponent made of silicon, wherein the lithium battery is formed in thesemiconductor substrate or in a layer over the semiconductor substrate.27. The electronic device according to claim 26, wherein the electronicdevice is selected from the group consisting of a sensor, an actuator,an RFID (radio frequency identification device) tag and a smartcard.